Silver halide system photography is superior to other photographic processes such as electrophotography and diazo processes in sensitivity and gradation adjustment and thus has heretofore been most widely used. In recent years, a technique which can easily and rapidly provide an image has been developed by changing the process for the formation of an image on a light-sensitive material from a wet process with a conventional developer or the like, to a dry process using heating or a like means.
Many methods for obtaining color images by heat development have been proposed. Methods which comprise bonding an oxidation product of a developing agent and a coupler to form a color image have been proposed in U.S. Pat. Nos. 3,531,286, 3,761,270, and 4,021,240, Belgian Patent 802,519, and Research Disclosure (Sep. 1975, page 32).
However, these methods are disadvantageous in that an image of reduced silver and a color image are formed on the heat-developed exposed portions at the same time, causing stain on the color image.
In order to eliminate this disadvantage, many approaches have been proposed, e.g., a method which comprises imagewise forming or releasing a mobile (diffusive) dye by heating, and then transferring the mobile dye to a dye fixing element having a mordant with a solvent such as water or a high boiling organic solvent or a hydrophilic heat solvent incorporated in the dye fixing element, and a method which comprises transferring a thermally-diffusive or sublimable dye to a dye receiving element such as support (U.S. Pat. Nos. 4,463,079, 4,474,867, 4,478,927, 4,507,380, 4,500,626, and 4,483,914, and JP-A-58-149046, JP-A-58-149047, JP-A-59-152440, JP-A-59-154445, JP-A-59-165054, JP-A-59-180548, JP-A-59-168439, JP-A-59-174832, JP-A-59-174833, JP-A-59-174834, and JP-A-59-174835 (the term "JP-A" as used herein means an "unexamined published Japanese patent application")).
In general, if two dye fixing elements on which an image has been formed by a transfer process such as the above mentioned image formation methods, are kept with the surfaces of their dye fixing layer sides opposed to each other, the dye image is retransferred to the opposing dye fixing layer. In particular, for the purpose of simplifying the development process, it is effective to incorporate a base or base precursor in a light-sensitive element or dye fixing element which is then subjected to heat development to form an image. However, "contact dye transfer" is worsened. Particularly, in the case where the base or base precursor is a water-soluble salt, "contact dye tranfer" is remarkably worsened.
In order to overcome this difficulty, the inventors previously proposed a dye fixing element comprising a nonionic water-soluble polysaccharide (particularly pullulan and dextran) in JP-A-62-47639 and a dye fixing element having a protective layer mainly comprising an anionic water-soluble polymer as an outermost layer in JP-A-63-103240.
The above mentioned methods have a remarkable effect on "contact dye transfer." However, if the light-sensitive material is stored under high humidity for prolonged period of time, its effect is not always sufficient. Thus, further improvements have been desired. A polymer dispersion having a glass transition temperature of 25.degree. C. or lower may be effectively incorporated into a dye fixing layer and/or an adjacent layer in a dye fixing element without a back layer as a curl balance layer to improve the curling properties. However, this worsens "contact dye transfer."
In general, means of inhibiting "contact dye transfer" cause deterioration of transferability during the image formation, often resulting in insufficient transfer density.